freshclam.log:

every hour a wake up signal is received:

Thu Mar 26 12:54:12 2020 -> Received signal: wake up
Thu Mar 26 12:54:12 2020 -> ClamAV update process started at Thu Mar 26 12:54:12 2020
Thu Mar 26 12:54:12 2020 -> daily.cld database is up to date (version: 25762, sigs: 2239415, f-level: 63, builder: raynman)
Thu Mar 26 12:54:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 12:54:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 12:54:12 2020 -> --------------------------------------
Thu Mar 26 13:54:12 2020 -> Received signal: wake up
Thu Mar 26 13:54:12 2020 -> ClamAV update process started at Thu Mar 26 13:54:12 2020
Thu Mar 26 13:54:12 2020 -> daily.cld database is up to date (version: 25762, sigs: 2239415, f-level: 63, builder: raynman)
Thu Mar 26 13:54:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 13:54:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 13:54:12 2020 -> --------------------------------------

then suddenly:

Thu Mar 26 14:54:12 2020 -> Received signal: wake up
Thu Mar 26 14:54:12 2020 -> ClamAV update process started at Thu Mar 26 14:54:12 2020
Thu Mar 26 14:54:12 2020 -> daily database available for update (local version: 25762, remote version: 25763)
Thu Mar 26 14:54:16 2020 -> Testing database: '/var/lib/clamav/tmp.e39fb/clamav-e406aa5ef0cc6a3c25bd248f692d0958.tmp-daily.cld' ...
Thu Mar 26 14:54:23 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (262144 bytes).
Thu Mar 26 14:54:23 2020 -> WARNING: [LibClamAV] hm_addhash_bin: failed to grow hash array to 1025 entries
Thu Mar 26 14:54:23 2020 -> WARNING: [LibClamAV] cli_loadhash: Malformed hash string at line 727354
Thu Mar 26 14:54:23 2020 -> WARNING: [LibClamAV] cli_loadhash: Problem parsing database at line 727354
Thu Mar 26 14:54:23 2020 -> WARNING: [LibClamAV] Can't load daily.hsb: Can't allocate memory
Thu Mar 26 14:54:23 2020 -> WARNING: [LibClamAV] cli_tgzload: Can't load daily.hsb
Thu Mar 26 14:54:23 2020 -> WARNING: [LibClamAV] Can't load /var/lib/clamav/tmp.e39fb/clamav-e406aa5ef0cc6a3c25bd248f692d0958.tmp-daily.cld: Malformed database
Thu Mar 26 14:54:23 2020 -> ERROR: Failed to load new database: Malformed database
Thu Mar 26 14:54:24 2020 -> WARNING: Database load exited with "Test failed" (8)
Thu Mar 26 14:54:24 2020 -> ERROR: Database test FAILED.
Thu Mar 26 14:54:24 2020 -> ERROR: Unexpected error when attempting to update database: daily
Thu Mar 26 14:54:24 2020 -> WARNING: fc_update_databases: fc_update_database failed: Test failed (8)
Thu Mar 26 14:54:24 2020 -> ERROR: Database update process failed: Test failed (8)
Thu Mar 26 14:54:24 2020 -> ERROR: Update failed.
Thu Mar 26 15:54:24 2020 -> Received signal: wake up
Thu Mar 26 15:54:24 2020 -> ClamAV update process started at Thu Mar 26 15:54:24 2020
Thu Mar 26 15:54:24 2020 -> daily database available for update (local version: 25762, remote version: 25763)
Thu Mar 26 15:54:28 2020 -> Testing database: '/var/lib/clamav/tmp.e39fb/clamav-3e50013c5b6bed641a847a24a38e1d41.tmp-daily.cld' ...
Thu Mar 26 15:54:35 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (262144 bytes).
Thu Mar 26 15:54:35 2020 -> WARNING: [LibClamAV] cli_mpool_strdup(): Can't allocate memory (28 bytes).
Thu Mar 26 15:54:35 2020 -> WARNING: [LibClamAV] cli_loadhash: Problem parsing database at line 741730
Thu Mar 26 15:54:35 2020 -> WARNING: [LibClamAV] Can't load daily.hsb: Malformed database
Thu Mar 26 15:54:35 2020 -> WARNING: [LibClamAV] cli_tgzload: Can't load daily.hsb
Thu Mar 26 15:54:35 2020 -> WARNING: [LibClamAV] Can't load /var/lib/clamav/tmp.e39fb/clamav-3e50013c5b6bed641a847a24a38e1d41.tmp-daily.cld: Malformed database
Thu Mar 26 15:54:35 2020 -> ERROR: Failed to load new database: Malformed database
Thu Mar 26 15:54:36 2020 -> WARNING: Database load exited with "Test failed" (8)
Thu Mar 26 15:54:36 2020 -> ERROR: Database test FAILED.
Thu Mar 26 15:54:36 2020 -> ERROR: Unexpected error when attempting to update database: daily
Thu Mar 26 15:54:36 2020 -> WARNING: fc_update_databases: fc_update_database failed: Test failed (8)
Thu Mar 26 15:54:36 2020 -> ERROR: Database update process failed: Test failed (8)
Thu Mar 26 15:54:36 2020 -> ERROR: Update failed.
Thu Mar 26 15:54:36 2020 -> --------------------------------------
Thu Mar 26 16:54:36 2020 -> Received signal: wake up
Thu Mar 26 16:54:36 2020 -> ClamAV update process started at Thu Mar 26 16:54:36 2020
Thu Mar 26 16:54:36 2020 -> daily database available for update (local version: 25762, remote version: 25763)
Thu Mar 26 16:54:39 2020 -> Testing database: '/var/lib/clamav/tmp.e39fb/clamav-4c1b79552e2bafd18d7486cdde7b7c92.tmp-daily.cld' ...
Thu Mar 26 16:54:45 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (262144 bytes).
Thu Mar 26 16:54:45 2020 -> WARNING: [LibClamAV] cli_mpool_strdup(): Can't allocate memory (28 bytes).
Thu Mar 26 16:54:45 2020 -> WARNING: [LibClamAV] cli_loadhash: Problem parsing database at line 719336
Thu Mar 26 16:54:45 2020 -> WARNING: [LibClamAV] Can't load daily.hsb: Malformed database
Thu Mar 26 16:54:45 2020 -> WARNING: [LibClamAV] cli_tgzload: Can't load daily.hsb
Thu Mar 26 16:54:45 2020 -> WARNING: [LibClamAV] Can't load /var/lib/clamav/tmp.e39fb/clamav-4c1b79552e2bafd18d7486cdde7b7c92.tmp-daily.cld: Malformed database
Thu Mar 26 16:54:45 2020 -> ERROR: Failed to load new database: Malformed database
Thu Mar 26 16:54:46 2020 -> WARNING: Database load exited with "Test failed" (8)
Thu Mar 26 16:54:46 2020 -> ERROR: Database test FAILED.
Thu Mar 26 16:54:46 2020 -> ERROR: Unexpected error when attempting to update database: daily
Thu Mar 26 16:54:46 2020 -> WARNING: fc_update_databases: fc_update_database failed: Test failed (8)
Thu Mar 26 16:54:46 2020 -> ERROR: Database update process failed: Test failed (8)
Thu Mar 26 16:54:46 2020 -> ERROR: Update failed.
Thu Mar 26 16:54:46 2020 -> --------------------------------------
Thu Mar 26 17:54:46 2020 -> Received signal: wake up
Thu Mar 26 17:54:46 2020 -> ClamAV update process started at Thu Mar 26 17:54:46 2020
Thu Mar 26 17:54:46 2020 -> daily database available for update (local version: 25762, remote version: 25763)
Thu Mar 26 17:54:49 2020 -> Testing database: '/var/lib/clamav/tmp.e39fb/clamav-ffbf12e684c64d7b8809b557c53d889a.tmp-daily.cld' ...Thu Mar 26 17:54:56 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (33558528 bytes).
Thu Mar 26 17:54:56 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (33558528 bytes).
Thu Mar 26 17:54:56 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (33558528 bytes).
Thu Mar 26 17:54:56 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (33558528 bytes).

....... more of these lines

Thu Mar 26 17:55:11 2020 -> WARNING: [LibClamAV] mpool_malloc(): Can't allocate memory (262144 bytes).
Thu Mar 26 17:55:11 2020 -> WARNING: [LibClamAV] cli_mpool_strdup(): Can't allocate memory (28 bytes).
Thu Mar 26 17:55:11 2020 -> WARNING: [LibClamAV] cli_loadhash: Problem parsing database at line 1210562
Thu Mar 26 17:55:11 2020 -> WARNING: [LibClamAV] Can't load daily.hsb: Malformed database
Thu Mar 26 17:55:11 2020 -> WARNING: [LibClamAV] cli_tgzload: Can't load daily.hsb
Thu Mar 26 17:55:11 2020 -> WARNING: [LibClamAV] Can't load /var/lib/clamav/tmp.e39fb/clamav-ffbf12e684c64d7b8809b557c53d889a.tmp-daily.cld: Malformed database
Thu Mar 26 17:55:11 2020 -> ERROR: Failed to load new database: Malformed database
Thu Mar 26 17:55:12 2020 -> Database test passed.
Thu Mar 26 17:55:12 2020 -> daily.cld updated (version: 25763, sigs: 2239743, f-level: 63, builder: raynman)
Thu Mar 26 17:55:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 17:55:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 17:55:12 2020 -> Clamd successfully notified about the update.
Thu Mar 26 17:55:12 2020 -> --------------------------------------

then back to normal

Thu Mar 26 18:55:12 2020 -> Received signal: wake up
Thu Mar 26 18:55:12 2020 -> ClamAV update process started at Thu Mar 26 18:55:12 2020
Thu Mar 26 18:55:12 2020 -> daily.cld database is up to date (version: 25763, sigs: 2239743, f-level: 63, builder: raynman)
Thu Mar 26 18:55:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 18:55:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 18:55:12 2020 -> --------------------------------------
Thu Mar 26 19:55:12 2020 -> Received signal: wake up
Thu Mar 26 19:55:12 2020 -> ClamAV update process started at Thu Mar 26 19:55:12 2020
Thu Mar 26 19:55:12 2020 -> daily.cld database is up to date (version: 25763, sigs: 2239743, f-level: 63, builder: raynman)
Thu Mar 26 19:55:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 19:55:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 19:55:12 2020 -> --------------------------------------
Thu Mar 26 20:55:12 2020 -> Received signal: wake up
Thu Mar 26 20:55:12 2020 -> ClamAV update process started at Thu Mar 26 20:55:12 2020
Thu Mar 26 20:55:12 2020 -> daily.cld database is up to date (version: 25763, sigs: 2239743, f-level: 63, builder: raynman)
Thu Mar 26 20:55:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 20:55:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 20:55:12 2020 -> --------------------------------------
Thu Mar 26 21:55:12 2020 -> Received signal: wake up
Thu Mar 26 21:55:12 2020 -> ClamAV update process started at Thu Mar 26 21:55:12 2020
Thu Mar 26 21:55:12 2020 -> daily.cld database is up to date (version: 25763, sigs: 2239743, f-level: 63, builder: raynman)
Thu Mar 26 21:55:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 21:55:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 21:55:12 2020 -> --------------------------------------
Thu Mar 26 22:55:12 2020 -> Received signal: wake up
Thu Mar 26 22:55:12 2020 -> ClamAV update process started at Thu Mar 26 22:55:12 2020
Thu Mar 26 22:55:12 2020 -> daily.cld database is up to date (version: 25763, sigs: 2239743, f-level: 63, builder: raynman)
Thu Mar 26 22:55:12 2020 -> main.cld database is up to date (version: 59, sigs: 4564902, f-level: 60, builder: sigmgr)
Thu Mar 26 22:55:12 2020 -> bytecode.cld database is up to date (version: 331, sigs: 94, f-level: 63, builder: anvilleg)
Thu Mar 26 22:55:12 2020 -> --------------------------------------

I have no idea what happens here. My system has 2 GB memory and 107 MB free.

 free -m
                      total        used        free      shared  buff/cache   available
Mem:           2004         504         107          36        1391        1321
Swap:             0              0              0

Any ideas?

Rgds
Dieter