failures, defects events, “human factors” or computer 
viruses events on time line, etc.  
To analyse an impact of information security on 
the  performance  of  standard  processes  there  are 
proposed the formalization for the general technology 
used in process performance. The technology is based 
on  periodical  diagnostics  of  modelled  system 
integrity, that is carried out to detect danger sources 
penetration into a modelled system or consequences 
of  negative  influences  (see  Figure  2).  The  lost 
modelled  system  integrity  can  be  detect  only  as  a 
result of diagnostics, after which the system recovery 
is started.  Dangerous influence on modelled system 
is  acted  step-by  step:  at  first  a  danger  source 
penetrates into the system and then after its activation 
begins to influence. The system integrity can’t be lost 
before  penetrated  danger  source  is  activated.  A 
danger is considered to be realized only after a danger 
source has influenced on the modelled system.
  
 
Figure 2: Some accident events in modelled system. 
(left – correct operation, right – a lose of integrity 
during prognostic period T
req
) 
There  are  recommended  some  “Black  box” 
models  for  which    probabilistic  space  (
,  B,  P)  is 
created  (see  for  example  Kostogryzov, 2008,  2012, 
2020 etc.), where: 
 - is a limited space of elementary 
events;  B  –  a  class  of  all  subspace  of 
-space, 
satisfied  to  the  properties  of 
-algebra;  P – is a 
probability measure on a space of elementary events 
.  Because, 
={
k
}  is  limited,  there  is  enough  to 
establish  a  reflection 
k
p
k
 =P(
k
)  like  that  p
k
0  
and 
1
k
k
p
.  
It is supposed that used diagnostic tools allow to 
provide  necessary  integrity  recovery after  revealing 
danger  sources  penetration into  modelled system  or 
the  consequences  of  influences.    Using  the 
probabilistic  models  (described  in  details  in 
Kostogryzov, 2008, 2012) the measures 𝑅
𝑇
 
 and 
𝑅
𝑇
 
  can  be  estimated  in  terms  “success”  or 
“failure”  considering  uncertainty  conditions, 
periodical  diagnostics,  monitoring  between 
diagnostics, recovery of the lost integrity for “Black 
box”.    There  are  the  next  input    for  probabilistic 
modeling (Kostogryzov, 2008-2020): 
 - frequency of the occurrences of potential 
threats  (or  mean  time  between  the  moments  of  the 
occurrences  of  potential  threats  which  equals  to 
1/frequency);  
  - mean activation time of threats;  
T
betw 
- time between the end of diagnostics and the 
beginning of the next diagnostics;  
T
diag
 - diagnostics time;  
T
recov
 - recovery time  
T - given prognostic period. 
3.2.2  About Modeling for Complex System 
For  a  complex    systems  with  parallel  or  serial 
structure  there  are  proposed  the  next  method  to 
generate  adequate  probabilistic  models 
(Kostogryzov, 2008-2020 etc.) This method uses the 
usual  way  of  probability  theory  for  independent 
random variables, it is described below.  
Let's consider the elementary structure from two 
independent parallel or series elements. Let’s PDF of 
time between  losses of i-th element integrity is В
i
(t) 
=Р (τ
i
≤ t), then:  
1) time between  losses of integrity for modelled 
system combined from series connected independent 
elements  is  equal  to  a  minimum from  two times  τ
i
: 
failure  of  1st  or  2nd  elements  (i.e.  the  modelled 
system goes into a state of lost integrity when either 
1st, or 2nd element integrity is lost).  For this case the 
PDF  of  time  between    losses  of  modelled  system 
integrity is defined by expression 
В(t) = Р[min (τ
1
,τ
2
)≤t] =1- Р[min (τ
1
,τ
2
)>t] = 
= 1- Р(τ
1
>t)Р(τ
2 
> t)= 1 – [1-В
1
(t)] [1- В
2
(t)],  (3) 
2) time between losses of integrity for modelled 
system  combined  from  parallel  connected 
independent elements (hot reservation) is equal to a 
maximum from two times τ
i
: failure  of 1st and 2nd 
elements (i.e. the modelled system goes into a state of 
lost integrity when both 1st and 2nd elements  have 
lost integrity).  For this case the PDF of time between  
losses  of  modelled  system  integrity  is  defined  by 
expression  
В(t)=Р[max(τ
1
,τ
2
)≤t]=Р(τ
1
≤t)Р(τ
2
≤t)=В
1
(t)В
2
(t)
 (4)  
Applying  recurrently  expressions  (3)  –  (4),  it  is 
possible  to  build  PDF  of  time  between    losses  of 
integrity for any complex system with parallel and/or 
series structure and theirs combinations. 
Using  these  probabilistic  models  and  methods 
(described  in  details  in  […])  the  measures 𝑅
𝑇
 
 
and 𝑅
𝑇
 
 can be  estimated  in  terms  “success”  or 
“failure” considering uncertainty conditions, system 
INFSEC 2021 - International Scientific and Practical Conference on Computer and Information Security